Skip to main content
U.S. flag

An official website of the United States government

Kaj Williams, Ph.D.

Kaj Williams is a planetary and atmospheric scientist at the USGS Astrogeology Science Center.

Science and Products

Filter Total Items: 14

It’s time for focused in situ studies of planetary surface-atmosphere interactions

A critical gap in planetary observations has been in situ characterization of extra-terrestrial, present-day atmospheric and surface environments and activity. While some surface activity has been observed and some in situ meteorological measurements have been collected by auxiliary instruments on Mars, existing information is insufficient to conclusively characterize the natural processes via con
Authors
Serina Diniega, Nathan Barba, Louis Giersch, Brian Jackson, Alejandro Soto, Don Banfield, Mackenzie D. Day, Gary Doran, Colin M. Dundas, Michael Mischna, Scot Rafkin, Isaac B. Smith, Rob Sullivan, Christy Swann, Timothy N. Titus, Ian J. Walker, Jacob Widmer, Devon M. Burr, Lukas Mandrake, Nathalie Vriend, Kaj E. Williams
By
Natural Hazards Mission Area, Astrogeology Science Center

The formation mechanisms for mid-latitude ice scarps on Mars

Mid-latitude exposed ice scarps have recently been identified on Mars (Dundas et al., 2018; 2021). The presence of such surface ice exposures at relatively low latitudes was itself a mystery, and the formation dynamics of such scarps have also not been explained. In this work we model the ice ablation rates of several identified mid-latitude scarps. We find that, given certain characteristics of t
Authors
Kaj E. Williams, Colin M. Dundas, Melinda A. Kahre
By
Natural Hazards Mission Area, Astrogeology Science Center

Fundamental science and engineering questions in planetary cave exploration

Nearly half a century ago, two papers postulated the likelihood of lunar lava tube caves using mathematical models. Today, armed with an array of orbiting and fly-by satellites and survey instrumentation, we have now acquired cave data across our solar system—including the identification of potential cave entrances on the Moon, Mars, and at least six other planetary bodies. These discoveries gave
Authors
J. Judson Wynne, Timothy N. Titus, Ali-akbar Agha-Mohammadi, Armando Azua-Bustos, Penelope J. Boston, Pablo de León, Cansu Demirel-Floyd, Jo de Waele, Heather Jones, Michael J. Malaska, Ana Z. Miller, Haley M. Sapers, Francesco Sauro, Derek L. Sonderegger, Kyle Uckert, Uland Y. Wong, E. Calvin Alexander, Leroy Chiao, Glen E. Cushing, John DeDecker, Alberto G. Fairén, Amos Frumkin, Gary L. Harris, Michelle L. Kearney, Laura A. Kerber, Richard J. Léveillé, Kavya Manyapu, Matteo Massironi, John E. Mylroie, Bogdan P. Onac, Scott E. Parazynski, Charity M. Phillips-Lander, T. H. Prettyman, Dirk Schulze-Makuch, Robert V. Wagner, William L. Whittaker, Kaj E. Williams
By
Natural Hazards Mission Area, Astrogeology Science Center

Mass balance of two perennial snowfields: Niwot Ridge, Colorado and the Ulaan Taiga, Mongolia.

Perennial snowfields are generally receding worldwide, though the precise mechanisms causing recessions are not always well understood. Here we apply a numerical snowpack model to identify the leading factors controlling the mass balance of two perennial snowfields that have significant human interest: Arapaho glacier, located at Niwot Ridge in the Colorado Rocky Mountains (United States), and a s
Authors
Kaj E. Williams, Christopher P. McKay, Owen B. Toon, Keith S. Jennings
By
Natural Hazards Mission Area, Climate Adaptation Science Centers, Astrogeology Science Center

A numerical model for the cooling of a lava sill with heat pipe effects

Understanding the cooling process of volcanic intrusions into wet sediments is a difficult but important problem, given the presence of extremely large temperature gradients and potentially complex water-magma interactions. This report presents a numerical model to study such interactions, including the effect of heat pipes on the cooling of volcanic intrusions. Udell (1985) has shown that heat pi
Authors
Kaj E. Williams, Colin M. Dundas, Laszlo P. Kestay
By
Natural Hazards Mission Area, Astrogeology Science Center

A roadmap for planetary caves science and exploration

While researchers have pondered the possibility of extraterrestrial caves for more than 50 years, we have now entered the incipient phase of planetary caves exploration. Our knowledge of planetary caves varies from body to body. Earth represents the most advanced level of exploration, but many unanswered questions remain. Beyond Earth, identification of possible caves is most advanced for the Moon
Authors
Timothy N. Titus, J. Judson Wynne, Michael J. Malaska, Ali-akbar Agha-Mohammadi, Peter Buhler, E. Calvin Alexander, James W. Ashley, Armando Azua-Bustos, Penelope J. Boston, Debra L. Buczkowski, Leroy Chiao, Glen E. Cushing, John DeDecker, Pablo de León, Cansu Demirel-Floyd, Jo de Waele, Alberto G. Fairén, Amos Frumkin, Gary L. Harris, Heather Jones, Laura H. Kerber, Erin J. Leonard, Richard J. Léveillé, Kavya Manyapu, Matteo Massironi, Ana Z. Miller, John E. Mylroie, Bogdan P. Onac, Scott E. Parazynski, Cynthia B. Phillips, Charity M. Phillips-Lander, Thomas H. Prettyman, Haley M. Sapers, Francesco Sauro, Norbert Schorghofer, Dirk Schulze-Makuch, Jennifer Scully, Kyle Uckert, Robert V. Wagner, William L. Whittaker, Kaj E. Williams, Uland Y. Wong
By
Natural Hazards Mission Area, Astrogeology Science Center

Aeolian processes and landforms across the Solar System: Science and technology requirements for the next decade

Discussions of planetary atmospheric-surface interactions (including aeolian processes and phenomena and the resulting landforms) are often tied to a specific planetary body. Considering this, a series of workshops were initiated in 2008 to facilitate an interdisciplinary and interplanetary body approach to further our understanding of aeolian processes, phenomena, and landforms (Titus et al., 200
Authors
Timothy N. Titus, S. Diniega, L.K. Fenton, Lynn D.V. Neakrase, J. Nienhuis, J Radebaugh, Kaj E. Williams, James R. Zimbelman
By
Natural Hazards Mission Area, Astrogeology Science Center

Science and technology requirements to explore caves in our Solar System

We are in the incipient phase of exploring the subterranean realm of our Solar System. Planetary caves research offers interdisciplinary, cross-planetary body investigations spanning geology, climatology, astrobiology, robotics, and human use. Caves are of great importance in advancing our understanding of planetary processes and the search for life beyond Earth. Given these advances, a diverse
Authors
Timothy N. Titus, Janna Wynne, P. J. Boston, P. de Leon, C. Demirel-Floyd, H Jones, Francesco Sauro, Kyle Uckert, Ali-akbar Agha-Mohammadi, E. Calvin Alexander, James W. Ashley, Armando Azua-Bustos, Leroy Chiao, Glen E. Cushing, J DeDecker, Alberto G. Fairén, A Frumkin, Jo de Waele, Gary L. Harris, Laura A. Kerber, Richard J. Léveillé, Michael J. Malaska, Kavya Manyapu, Matteo Massironi, Ana Z. Miller, John E. Mylroie, Bogdan P. Onac, Scott Parazynski, Charity Phillips-Lander, Thomas Prettyman, Haley Sapers, Norbert Schorghofer, Dirk Schulze-Makuch, Red Whittaker, Kaj E. Williams, Uland Wong
By
Natural Hazards Mission Area, Astrogeology Science Center

A critical gap: In situ measurements of surface-atmosphere interactions from outside earth

This white paper demonstrates five points: (1) The lack of robust measurements of the vertical gradients of natural boundary layers and transport fluxes on other planetary bodies precludes adequate estimation of aeolian and other meteorological processes throughout our Solar System (§1). (2) Thus, there exist critical knowledge gaps within high-priority planetary science questions that motivate th
Authors
Serina Diniega, Devon M. Burr, Colin M. Dundas, Brian Jackson, Michael Mischna, Scot Rafkin, Isaac B. Smith, Robert Sullivan, Timothy N. Titus, Nathalie Vriend, Ian J. Walker, Kaj E. Williams
By
Natural Hazards Mission Area, Astrogeology Science Center

Mars Astrobiological Cave and Internal habitability Explorer (MACIE): A New Frontiers mission concept

Martian subsurface habitability and astrobiology can be evaluated via a lava tube cave, without drilling. MACIE addresses two key goals of the Decadal Survey (2013–2022) and three MEPAG goals. New advances in robotic architectures, autonomous navigation, target sample selection, and analysis will enable MACIE to explore the Martian subsurface.
Authors
C. M. Phillips-Lander, A. Agha-mohamamdi, J. J. Wynne, Timothy N. Titus, N. Chanover, C. Demirel-Floyd, Kyle Uckert, Kaj E. Williams, D Wyrick, J. Blank, Penelope J. Boston, K. Mitchell, A Kereszturi, J. Martin-Torres, S. Shkolyar, N. Bardabelias, S. Datta, K. Retherford, Lydia Sam, A. Bahardwaj, A. Fairén, D. Flannery, Roger C. Wiens
By
Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center

Widespread exposures of extensive clean shallow ice in the mid-latitudes of Mars

Although ice in the Martian midlatitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50° and 61° north and south latitude and that they are concentrated in and near Milankovič crater i
Authors
Colin M. Dundas, Michael T. Mellon, Susan J. Conway, Ingrid J. Daubar, Kaj E. Williams, Lujendra Ojha, James J. Wray, Ali Bramson, Shane Byrne, Alfred S. McEwen, Liliya Posiolova, Gunnar Speth, Donna Viola, Margaret E. Landis, Gareth A Morgan, Asmin V Pathare
By
Natural Hazards Mission Area, Astrogeology Science Center

Conceptual model for the removal of cold-trapped H2O ice on the Mars northern seasonal springtime polar cap

The transport of H2O ice along the retreating north polar seasonal CO2 ice cap has previously been modeled and observed. Spectral observations show that H2O ice forms on the interior of the seasonal cap, while thermal observations show these regions to be consistent with CO2 ice. Prior to the sublimation of the seasonal CO2, the observed H2O ice deposits are diminished—and because H2O ice sublimat
Authors
Timothy N. Titus, Kaj E. Williams, Glen E. Cushing
By
Natural Hazards Mission Area, Astrogeology Science Center

Non-USGS Publications**

Williams, Kaj, Christopher P. McKay and J.L Heldmann. (2015) Modeling the effects of Martian surface frost on ice table depth. Icarus, 261, 58-65.
Williams, Kaj and Chris McKay. (2015). Comparing flow-through and static ice cave models for Shoshone Ice Cave. International Journal of Speleology, 44: 1.
Heldmann, J. L., W. Pollard, C. P. Mckay, M. M. Marinova, A. Davila, K. E. Williams, D. Lacelle, and D. T. Andersen (2013), The high elevation Dry Valleys in Antarctica as analog sites for subsurface ice on Mars, Planetary and Space Science, 85(C), doi:10.1016/j.pss.2013.05.019.
J.L. Heldmann, M. Marinova, K.E. Williams, D. Lacelle, C.P. McKay, A. Davila, W. Pollard and D.T. Andersen (2012). Formation and evolution of buried snowpack deposits in Pearse Valley, Antarctica, and implications for Mars. Antarctic Science, 24, doi:10.1017/S0954102011000903
Williams, K. E., McKay, C. P. and Persson, F. (2012) The surface energy balance at the Huygens Landing site and the moist surface conditions on Titan. Planetary and Space Science. Vol 60, nr. 1.
Williams, K. E., Pappalardo, R. T. (2011) Variability in the Small Crater Population of Callisto. Icarus 215,1.
Williams, K.E., McKay, C. P., Toon, O.B., Head, J. W. (2010) Do Ice Caves Exist on Mars? Icarus 209,2.
Williams, K.E., Toon, O. B., Heldmann, J. L., Mellon, M. (2009) Ancient melting of mid-latitude snowpacks on Mars as a water source for gullies, Icarus, 200.
Williams, K.E., Toon, O.B., Heldmann, J.L. , McKay C.P. and Mellon, M. (2008) Stability of Mid-Latitude Snowpacks on Mars, Icarus, 196.
Williams, K. E., O. B. Toon, and J. Heldmann (2007), Modeling water ice lifetimes at recent Martian gully locations, Geophys. Res. Lett., 34, L09204, doi:10.1029/2007GL029507.
Lai, Y.C., Lerner, D, Williams, K and Crebogi, C. (Nov. 1999) Unstable dimension variability in coupled chaotic systems. Physical Review E 60 (5): 5445-5454 : A.

**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.

link
Photo of a large, deep, circular depression in the desert with an elevated rim

Planetary Defense

At the USGS Astrogeology Science Center we conduct research on Planetary Defense. Planetary Defense involves predicting potential impactors (asteroids, comets), and studying how to deflect or divert them, as well as the potential effects of an impact. Effects include short-term effects such as blast damage, but also long-term effects such as climate and social impacts.
By
Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center
link

Planetary Defense

At the USGS Astrogeology Science Center we conduct research on Planetary Defense. Planetary Defense involves predicting potential impactors (asteroids, comets), and studying how to deflect or divert them, as well as the potential effects of an impact. Effects include short-term effects such as blast damage, but also long-term effects such as climate and social impacts.
Learn More
link
Great Sand Dunes

Surface - Atmosphere interaction

The USGS Astrogeology Science Center conducts research on the interaction between planetary surfaces and the overlying atmospheres. In particular, the transfer of momentum (from wind), vapor (evaporation/sublimation), liquid (rainfall, percolation, infiltration) and solids (snow) occurs between surfaces and atmospheres.
By
Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center
link

Surface - Atmosphere interaction

The USGS Astrogeology Science Center conducts research on the interaction between planetary surfaces and the overlying atmospheres. In particular, the transfer of momentum (from wind), vapor (evaporation/sublimation), liquid (rainfall, percolation, infiltration) and solids (snow) occurs between surfaces and atmospheres.
Learn More
link
snow and a small stream

Planetary Volatiles: Snow and Ice

The USGS Astrogeology Science Center conducts research on planetary volatiles. Volatiles include substances that have a high vapor pressure relative to the ambient atmosphere. We study the longevity, locations and other characteristics of volatiles. More specifically: H2O ice, snow and frost are volatiles on the Earth. We study the persistence of perennial snowfields in Colorado and Mongolia. Mars...
By
Core Science Systems Mission Area, Ecosystems Mission Area, Natural Hazards Mission Area, Water Resources Mission Area, Astrogeology Science Center
link

Planetary Volatiles: Snow and Ice

The USGS Astrogeology Science Center conducts research on planetary volatiles. Volatiles include substances that have a high vapor pressure relative to the ambient atmosphere. We study the longevity, locations and other characteristics of volatiles. More specifically: H2O ice, snow and frost are volatiles on the Earth. We study the persistence of perennial snowfields in Colorado and Mongolia. Mars...
Learn More
link
A photo taken from within Nāhuku (Thurston Lava Tube), near the summit of Kīlauea

Caves

The USGS Astrogeology Science Center conducts research on caves. In particular, we are interested in the physics of caves, which involves the application of the principles of heat transfer, mass transfer and meteorology to understand how cave climates evolve. We are also interested in caves on other planetary bodies and moons, and how they may be used as resources for future missions.
By
Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center
link

Caves

The USGS Astrogeology Science Center conducts research on caves. In particular, we are interested in the physics of caves, which involves the application of the principles of heat transfer, mass transfer and meteorology to understand how cave climates evolve. We are also interested in caves on other planetary bodies and moons, and how they may be used as resources for future missions.
Learn More
link
SP Crater Arizona

Terrestrial Analogs for Research and Geologic Exploration Training (TARGET)​

The U. S. Geological Survey (USGS) Astrogeology Science Center (ASC) recently established the Terrestrial Analogs for Research and Geologic Exploration Training (TARGET) program. This service-oriented program is built around the recognition that the Earth is a fundamental training ground for human and robotic planetary exploration, and that ASC is in a unique position in northern Arizona with...
By
Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center, Planetary Geologic Mapping
link

Terrestrial Analogs for Research and Geologic Exploration Training (TARGET)​

The U. S. Geological Survey (USGS) Astrogeology Science Center (ASC) recently established the Terrestrial Analogs for Research and Geologic Exploration Training (TARGET) program. This service-oriented program is built around the recognition that the Earth is a fundamental training ground for human and robotic planetary exploration, and that ASC is in a unique position in northern Arizona with...
Learn More

Subsurface temperature profiles, imagery, and meteorological data at a Sunset Crater cinder field: March 2021 to May 2022

We have set up a meteorological station at a small cinder field in Sunset Crater National Monument, Arizona, that records temperature, barometric pressure, relative humidity, wind direction, wind speed, solar radiation, and precipitation. Each hour, a BlazeVideo camera records a small portion of the cinder field adjacent to the meteorological station. Subsurface temperatures are recorded at cinder
By
Astrogeology Science Center

Imagery and meteorological data from April 2021 to December 2021, Grand Falls Dune Field, Arizona

Grand Falls dune field (GFDF) is located on the Navajo Nation, ~70 km NE of Flagstaff, AZ. This active dune field displays a range of morphologies, including barchans, smaller dunes, and ripples, and is bimodal in composition. The felsic component is likely derived from the Little Colorado River, and the mafic component (basaltic grains) is locally sourced from nearby cinder cones [1]. GFDF is an
By
Astrogeology Science Center

Imagery, soil temperature and humidity profiles, and meteorological data from December 2020 to April 2021, Grand Falls Dune Field, Arizona

Grand Falls dune field (GFDF) is located on the Navajo Nation, ~70 km NE of Flagstaff, AZ. This active dune field displays a range of morphologies, including barchans, smaller dunes, and ripples, and is bimodal in composition. The felsic component is likely derived from the Little Colorado River, and the mafic component (basaltic grains) is locally sourced from nearby cinder cones [1]. GFDF is an
By
Astrogeology Science Center

Locations and Properties of Ice-Exposing Scarps and New Impact Craters in the Mid-Latitudes of Mars

Although ice in the Martian mid-latitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50-61 north and south latitude, and that they are concentrated in and near Milankovi crater in the
By
Astrogeology Science Center
link

Caves Across the Solar System

Are you curious about extraterrestrial caves? Do you wonder what’s inside of these cave systems and how they were formed? We’ve reached out to...

Read Article

Science and Products

  • Publications
    Filter Total Items: 14

    It’s time for focused in situ studies of planetary surface-atmosphere interactions

    A critical gap in planetary observations has been in situ characterization of extra-terrestrial, present-day atmospheric and surface environments and activity. While some surface activity has been observed and some in situ meteorological measurements have been collected by auxiliary instruments on Mars, existing information is insufficient to conclusively characterize the natural processes via con
    Authors
    Serina Diniega, Nathan Barba, Louis Giersch, Brian Jackson, Alejandro Soto, Don Banfield, Mackenzie D. Day, Gary Doran, Colin M. Dundas, Michael Mischna, Scot Rafkin, Isaac B. Smith, Rob Sullivan, Christy Swann, Timothy N. Titus, Ian J. Walker, Jacob Widmer, Devon M. Burr, Lukas Mandrake, Nathalie Vriend, Kaj E. Williams
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    The formation mechanisms for mid-latitude ice scarps on Mars

    Mid-latitude exposed ice scarps have recently been identified on Mars (Dundas et al., 2018; 2021). The presence of such surface ice exposures at relatively low latitudes was itself a mystery, and the formation dynamics of such scarps have also not been explained. In this work we model the ice ablation rates of several identified mid-latitude scarps. We find that, given certain characteristics of t
    Authors
    Kaj E. Williams, Colin M. Dundas, Melinda A. Kahre
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    Fundamental science and engineering questions in planetary cave exploration

    Nearly half a century ago, two papers postulated the likelihood of lunar lava tube caves using mathematical models. Today, armed with an array of orbiting and fly-by satellites and survey instrumentation, we have now acquired cave data across our solar system—including the identification of potential cave entrances on the Moon, Mars, and at least six other planetary bodies. These discoveries gave
    Authors
    J. Judson Wynne, Timothy N. Titus, Ali-akbar Agha-Mohammadi, Armando Azua-Bustos, Penelope J. Boston, Pablo de León, Cansu Demirel-Floyd, Jo de Waele, Heather Jones, Michael J. Malaska, Ana Z. Miller, Haley M. Sapers, Francesco Sauro, Derek L. Sonderegger, Kyle Uckert, Uland Y. Wong, E. Calvin Alexander, Leroy Chiao, Glen E. Cushing, John DeDecker, Alberto G. Fairén, Amos Frumkin, Gary L. Harris, Michelle L. Kearney, Laura A. Kerber, Richard J. Léveillé, Kavya Manyapu, Matteo Massironi, John E. Mylroie, Bogdan P. Onac, Scott E. Parazynski, Charity M. Phillips-Lander, T. H. Prettyman, Dirk Schulze-Makuch, Robert V. Wagner, William L. Whittaker, Kaj E. Williams
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    Mass balance of two perennial snowfields: Niwot Ridge, Colorado and the Ulaan Taiga, Mongolia.

    Perennial snowfields are generally receding worldwide, though the precise mechanisms causing recessions are not always well understood. Here we apply a numerical snowpack model to identify the leading factors controlling the mass balance of two perennial snowfields that have significant human interest: Arapaho glacier, located at Niwot Ridge in the Colorado Rocky Mountains (United States), and a s
    Authors
    Kaj E. Williams, Christopher P. McKay, Owen B. Toon, Keith S. Jennings
    By
    Natural Hazards Mission Area, Climate Adaptation Science Centers, Astrogeology Science Center

    A numerical model for the cooling of a lava sill with heat pipe effects

    Understanding the cooling process of volcanic intrusions into wet sediments is a difficult but important problem, given the presence of extremely large temperature gradients and potentially complex water-magma interactions. This report presents a numerical model to study such interactions, including the effect of heat pipes on the cooling of volcanic intrusions. Udell (1985) has shown that heat pi
    Authors
    Kaj E. Williams, Colin M. Dundas, Laszlo P. Kestay
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    A roadmap for planetary caves science and exploration

    While researchers have pondered the possibility of extraterrestrial caves for more than 50 years, we have now entered the incipient phase of planetary caves exploration. Our knowledge of planetary caves varies from body to body. Earth represents the most advanced level of exploration, but many unanswered questions remain. Beyond Earth, identification of possible caves is most advanced for the Moon
    Authors
    Timothy N. Titus, J. Judson Wynne, Michael J. Malaska, Ali-akbar Agha-Mohammadi, Peter Buhler, E. Calvin Alexander, James W. Ashley, Armando Azua-Bustos, Penelope J. Boston, Debra L. Buczkowski, Leroy Chiao, Glen E. Cushing, John DeDecker, Pablo de León, Cansu Demirel-Floyd, Jo de Waele, Alberto G. Fairén, Amos Frumkin, Gary L. Harris, Heather Jones, Laura H. Kerber, Erin J. Leonard, Richard J. Léveillé, Kavya Manyapu, Matteo Massironi, Ana Z. Miller, John E. Mylroie, Bogdan P. Onac, Scott E. Parazynski, Cynthia B. Phillips, Charity M. Phillips-Lander, Thomas H. Prettyman, Haley M. Sapers, Francesco Sauro, Norbert Schorghofer, Dirk Schulze-Makuch, Jennifer Scully, Kyle Uckert, Robert V. Wagner, William L. Whittaker, Kaj E. Williams, Uland Y. Wong
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    Aeolian processes and landforms across the Solar System: Science and technology requirements for the next decade

    Discussions of planetary atmospheric-surface interactions (including aeolian processes and phenomena and the resulting landforms) are often tied to a specific planetary body. Considering this, a series of workshops were initiated in 2008 to facilitate an interdisciplinary and interplanetary body approach to further our understanding of aeolian processes, phenomena, and landforms (Titus et al., 200
    Authors
    Timothy N. Titus, S. Diniega, L.K. Fenton, Lynn D.V. Neakrase, J. Nienhuis, J Radebaugh, Kaj E. Williams, James R. Zimbelman
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    Science and technology requirements to explore caves in our Solar System

    We are in the incipient phase of exploring the subterranean realm of our Solar System. Planetary caves research offers interdisciplinary, cross-planetary body investigations spanning geology, climatology, astrobiology, robotics, and human use. Caves are of great importance in advancing our understanding of planetary processes and the search for life beyond Earth. Given these advances, a diverse
    Authors
    Timothy N. Titus, Janna Wynne, P. J. Boston, P. de Leon, C. Demirel-Floyd, H Jones, Francesco Sauro, Kyle Uckert, Ali-akbar Agha-Mohammadi, E. Calvin Alexander, James W. Ashley, Armando Azua-Bustos, Leroy Chiao, Glen E. Cushing, J DeDecker, Alberto G. Fairén, A Frumkin, Jo de Waele, Gary L. Harris, Laura A. Kerber, Richard J. Léveillé, Michael J. Malaska, Kavya Manyapu, Matteo Massironi, Ana Z. Miller, John E. Mylroie, Bogdan P. Onac, Scott Parazynski, Charity Phillips-Lander, Thomas Prettyman, Haley Sapers, Norbert Schorghofer, Dirk Schulze-Makuch, Red Whittaker, Kaj E. Williams, Uland Wong
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    A critical gap: In situ measurements of surface-atmosphere interactions from outside earth

    This white paper demonstrates five points: (1) The lack of robust measurements of the vertical gradients of natural boundary layers and transport fluxes on other planetary bodies precludes adequate estimation of aeolian and other meteorological processes throughout our Solar System (§1). (2) Thus, there exist critical knowledge gaps within high-priority planetary science questions that motivate th
    Authors
    Serina Diniega, Devon M. Burr, Colin M. Dundas, Brian Jackson, Michael Mischna, Scot Rafkin, Isaac B. Smith, Robert Sullivan, Timothy N. Titus, Nathalie Vriend, Ian J. Walker, Kaj E. Williams
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    Mars Astrobiological Cave and Internal habitability Explorer (MACIE): A New Frontiers mission concept

    Martian subsurface habitability and astrobiology can be evaluated via a lava tube cave, without drilling. MACIE addresses two key goals of the Decadal Survey (2013–2022) and three MEPAG goals. New advances in robotic architectures, autonomous navigation, target sample selection, and analysis will enable MACIE to explore the Martian subsurface.
    Authors
    C. M. Phillips-Lander, A. Agha-mohamamdi, J. J. Wynne, Timothy N. Titus, N. Chanover, C. Demirel-Floyd, Kyle Uckert, Kaj E. Williams, D Wyrick, J. Blank, Penelope J. Boston, K. Mitchell, A Kereszturi, J. Martin-Torres, S. Shkolyar, N. Bardabelias, S. Datta, K. Retherford, Lydia Sam, A. Bahardwaj, A. Fairén, D. Flannery, Roger C. Wiens
    By
    Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center

    Widespread exposures of extensive clean shallow ice in the mid-latitudes of Mars

    Although ice in the Martian midlatitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50° and 61° north and south latitude and that they are concentrated in and near Milankovič crater i
    Authors
    Colin M. Dundas, Michael T. Mellon, Susan J. Conway, Ingrid J. Daubar, Kaj E. Williams, Lujendra Ojha, James J. Wray, Ali Bramson, Shane Byrne, Alfred S. McEwen, Liliya Posiolova, Gunnar Speth, Donna Viola, Margaret E. Landis, Gareth A Morgan, Asmin V Pathare
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    Conceptual model for the removal of cold-trapped H2O ice on the Mars northern seasonal springtime polar cap

    The transport of H2O ice along the retreating north polar seasonal CO2 ice cap has previously been modeled and observed. Spectral observations show that H2O ice forms on the interior of the seasonal cap, while thermal observations show these regions to be consistent with CO2 ice. Prior to the sublimation of the seasonal CO2, the observed H2O ice deposits are diminished—and because H2O ice sublimat
    Authors
    Timothy N. Titus, Kaj E. Williams, Glen E. Cushing
    By
    Natural Hazards Mission Area, Astrogeology Science Center

    Non-USGS Publications**

    Williams, Kaj, Christopher P. McKay and J.L Heldmann. (2015) Modeling the effects of Martian surface frost on ice table depth. Icarus, 261, 58-65.
    Williams, Kaj and Chris McKay. (2015). Comparing flow-through and static ice cave models for Shoshone Ice Cave. International Journal of Speleology, 44: 1.
    Heldmann, J. L., W. Pollard, C. P. Mckay, M. M. Marinova, A. Davila, K. E. Williams, D. Lacelle, and D. T. Andersen (2013), The high elevation Dry Valleys in Antarctica as analog sites for subsurface ice on Mars, Planetary and Space Science, 85(C), doi:10.1016/j.pss.2013.05.019.
    J.L. Heldmann, M. Marinova, K.E. Williams, D. Lacelle, C.P. McKay, A. Davila, W. Pollard and D.T. Andersen (2012). Formation and evolution of buried snowpack deposits in Pearse Valley, Antarctica, and implications for Mars. Antarctic Science, 24, doi:10.1017/S0954102011000903
    Williams, K. E., McKay, C. P. and Persson, F. (2012) The surface energy balance at the Huygens Landing site and the moist surface conditions on Titan. Planetary and Space Science. Vol 60, nr. 1.
    Williams, K. E., Pappalardo, R. T. (2011) Variability in the Small Crater Population of Callisto. Icarus 215,1.
    Williams, K.E., McKay, C. P., Toon, O.B., Head, J. W. (2010) Do Ice Caves Exist on Mars? Icarus 209,2.
    Williams, K.E., Toon, O. B., Heldmann, J. L., Mellon, M. (2009) Ancient melting of mid-latitude snowpacks on Mars as a water source for gullies, Icarus, 200.
    Williams, K.E., Toon, O.B., Heldmann, J.L. , McKay C.P. and Mellon, M. (2008) Stability of Mid-Latitude Snowpacks on Mars, Icarus, 196.
    Williams, K. E., O. B. Toon, and J. Heldmann (2007), Modeling water ice lifetimes at recent Martian gully locations, Geophys. Res. Lett., 34, L09204, doi:10.1029/2007GL029507.
    Lai, Y.C., Lerner, D, Williams, K and Crebogi, C. (Nov. 1999) Unstable dimension variability in coupled chaotic systems. Physical Review E 60 (5): 5445-5454 : A.

    **Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.

  • Science
    link
    Photo of a large, deep, circular depression in the desert with an elevated rim

    Planetary Defense

    At the USGS Astrogeology Science Center we conduct research on Planetary Defense. Planetary Defense involves predicting potential impactors (asteroids, comets), and studying how to deflect or divert them, as well as the potential effects of an impact. Effects include short-term effects such as blast damage, but also long-term effects such as climate and social impacts.
    By
    Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center
    link

    Planetary Defense

    At the USGS Astrogeology Science Center we conduct research on Planetary Defense. Planetary Defense involves predicting potential impactors (asteroids, comets), and studying how to deflect or divert them, as well as the potential effects of an impact. Effects include short-term effects such as blast damage, but also long-term effects such as climate and social impacts.
    Learn More
    link
    Great Sand Dunes

    Surface - Atmosphere interaction

    The USGS Astrogeology Science Center conducts research on the interaction between planetary surfaces and the overlying atmospheres. In particular, the transfer of momentum (from wind), vapor (evaporation/sublimation), liquid (rainfall, percolation, infiltration) and solids (snow) occurs between surfaces and atmospheres.
    By
    Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center
    link

    Surface - Atmosphere interaction

    The USGS Astrogeology Science Center conducts research on the interaction between planetary surfaces and the overlying atmospheres. In particular, the transfer of momentum (from wind), vapor (evaporation/sublimation), liquid (rainfall, percolation, infiltration) and solids (snow) occurs between surfaces and atmospheres.
    Learn More
    link
    snow and a small stream

    Planetary Volatiles: Snow and Ice

    The USGS Astrogeology Science Center conducts research on planetary volatiles. Volatiles include substances that have a high vapor pressure relative to the ambient atmosphere. We study the longevity, locations and other characteristics of volatiles. More specifically: H2O ice, snow and frost are volatiles on the Earth. We study the persistence of perennial snowfields in Colorado and Mongolia. Mars...
    By
    Core Science Systems Mission Area, Ecosystems Mission Area, Natural Hazards Mission Area, Water Resources Mission Area, Astrogeology Science Center
    link

    Planetary Volatiles: Snow and Ice

    The USGS Astrogeology Science Center conducts research on planetary volatiles. Volatiles include substances that have a high vapor pressure relative to the ambient atmosphere. We study the longevity, locations and other characteristics of volatiles. More specifically: H2O ice, snow and frost are volatiles on the Earth. We study the persistence of perennial snowfields in Colorado and Mongolia. Mars...
    Learn More
    link
    A photo taken from within Nāhuku (Thurston Lava Tube), near the summit of Kīlauea

    Caves

    The USGS Astrogeology Science Center conducts research on caves. In particular, we are interested in the physics of caves, which involves the application of the principles of heat transfer, mass transfer and meteorology to understand how cave climates evolve. We are also interested in caves on other planetary bodies and moons, and how they may be used as resources for future missions.
    By
    Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center
    link

    Caves

    The USGS Astrogeology Science Center conducts research on caves. In particular, we are interested in the physics of caves, which involves the application of the principles of heat transfer, mass transfer and meteorology to understand how cave climates evolve. We are also interested in caves on other planetary bodies and moons, and how they may be used as resources for future missions.
    Learn More
    link
    SP Crater Arizona

    Terrestrial Analogs for Research and Geologic Exploration Training (TARGET)​

    The U. S. Geological Survey (USGS) Astrogeology Science Center (ASC) recently established the Terrestrial Analogs for Research and Geologic Exploration Training (TARGET) program. This service-oriented program is built around the recognition that the Earth is a fundamental training ground for human and robotic planetary exploration, and that ASC is in a unique position in northern Arizona with...
    By
    Core Science Systems Mission Area, Natural Hazards Mission Area, Astrogeology Science Center, Planetary Geologic Mapping
    link

    Terrestrial Analogs for Research and Geologic Exploration Training (TARGET)​

    The U. S. Geological Survey (USGS) Astrogeology Science Center (ASC) recently established the Terrestrial Analogs for Research and Geologic Exploration Training (TARGET) program. This service-oriented program is built around the recognition that the Earth is a fundamental training ground for human and robotic planetary exploration, and that ASC is in a unique position in northern Arizona with...
    Learn More
  • Data

    Subsurface temperature profiles, imagery, and meteorological data at a Sunset Crater cinder field: March 2021 to May 2022

    We have set up a meteorological station at a small cinder field in Sunset Crater National Monument, Arizona, that records temperature, barometric pressure, relative humidity, wind direction, wind speed, solar radiation, and precipitation. Each hour, a BlazeVideo camera records a small portion of the cinder field adjacent to the meteorological station. Subsurface temperatures are recorded at cinder
    By
    Astrogeology Science Center

    Imagery and meteorological data from April 2021 to December 2021, Grand Falls Dune Field, Arizona

    Grand Falls dune field (GFDF) is located on the Navajo Nation, ~70 km NE of Flagstaff, AZ. This active dune field displays a range of morphologies, including barchans, smaller dunes, and ripples, and is bimodal in composition. The felsic component is likely derived from the Little Colorado River, and the mafic component (basaltic grains) is locally sourced from nearby cinder cones [1]. GFDF is an
    By
    Astrogeology Science Center

    Imagery, soil temperature and humidity profiles, and meteorological data from December 2020 to April 2021, Grand Falls Dune Field, Arizona

    Grand Falls dune field (GFDF) is located on the Navajo Nation, ~70 km NE of Flagstaff, AZ. This active dune field displays a range of morphologies, including barchans, smaller dunes, and ripples, and is bimodal in composition. The felsic component is likely derived from the Little Colorado River, and the mafic component (basaltic grains) is locally sourced from nearby cinder cones [1]. GFDF is an
    By
    Astrogeology Science Center

    Locations and Properties of Ice-Exposing Scarps and New Impact Craters in the Mid-Latitudes of Mars

    Although ice in the Martian mid-latitudes is typically covered by a layer of dust or regolith, it is exposed in some locations by fresh impact craters or in erosional scarps. In both cases, the exposed ice is massive or excess ice with a low lithic content. We find that erosional scarps occur between 50-61 north and south latitude, and that they are concentrated in and near Milankovi crater in the
    By
    Astrogeology Science Center
  • News
    link

    Caves Across the Solar System

    Are you curious about extraterrestrial caves? Do you wonder what’s inside of these cave systems and how they were formed? We’ve reached out to...

    Read Article